The transmissions may be better, or may not be. Time will tell. I can tell you the 300 series are 1) beastly large and heavy,2) expensive, and 3) not worth two cents on a hill side. Plus if you buy one you get a company who will refuse to acknowledge obvious design flaws. The ZD21, and apparently 28 mowers should have been recalled and the drive trains replaced with a redesigned drive train at Kubota's expense.
I wonder how many of those mowers they would have sold had had they promoted "The ZD's are pretty good mowers but never use them on a hill side, as this will certainly result in total transmission failure". Maybe they should have mounted bubble levels on the front of the mowers. That way as soon as the bubble indicated any type of incline you could immediately shut the mower off and tow it back to level ground.
I wonder how many of those mowers they would have sold had had they promoted "The ZD's are pretty good mowers but never use them on a hill side, as this will certainly result in total transmission failure". Maybe they should have mounted bubble levels on the front of the mowers. That way as soon as the bubble indicated any type of incline you could immediately shut the mower off and tow it back to level ground.